Antenna for aircraft



M3 8 2 ssmw m Get. 18, 1949 3L K. as; ARMQN 254341317 ANTENNA FORAIRGHAFT Filed D90. 15, 1942 3 Sheets-Sheet l J. K. DE ARMOND A 7TOHNEYSEARCH RGUN Oct. 18, 19491. J. K. DE ARMQND ANTENNA FOR AIRCRAFT-1 sSheets-Sheet '3 Filed Dec. 15, 19 42 J. K175 ARMOND ATTORNEY PatentedOct. 18, 1949 blllilititl ttUUllil UNITED STATES PATENT OFFICE (Grantedunder the act of March 3, 1883, as amended April 30, 1928; 370 0. G.757) 4 Claims.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes, without the payment to me ofany royalty thereon.

This invention relates to an antenna system for aircraft.

One object of this invention is to provide a system for easily adjustingthe height of an antenna for tuning, by protecting the antenna from windstresses.

Another object of this invention is to provide a housing to surround theactive antenna element.

The construction and the arrangement of the various parts of the system,including the antenna and its control equipment, are illustrated in theaccompanying drawings, in which:

Figure 1 is a schematic perspective view showing the function anddisposition of the various parts of the equipment for controlling theantenna;

Figure 2 is a schematic side view of an airplane, showing the relativedisposition of the antenna;

Figure 3 is a front elevational view of the antenna and the upper end ofthe mast housing for the antenna with the front of the mast housingbroken away to show the antenna;

Figure 4 is a schematic end view of the several cam and switchassemblies, showin their relative positions at one selected instant;

Figure 5 is a diagramatic circuit of the operating motor for the antennasystem, and illustrates the arrangement of the control switches in theassemblies in Figure 4;

Figures 6, 7, and 8 are perspective views of one of the cam and switch.assemblies showing the provision of travel limiting stops forcontrolling the associated cams.

As shown in Figure l, a control system for an antenna, that isparticularly to be employed in aircraft, is illustrated as including areversible motor I l, whose operating energy is derived from a suitablesource or circuit H, to operate a train of gear mechanism, to adjustablyposition an antenna mast l3 at any one of a number of preselectedpositions that will provide an antenna of suitable length to receiveradiant energy of a pre-selected frequency. The gear train forcontrolling the antenna I3 is shown as comprising i a worm I4 on themotor shaft, and worm gear l meshed with the worm I4, and a sprocketwheel I6 provided with sprocket teeth l6-a that fit into spaced sprocketopenings l3-a centrally along the length of the antenna mast I3.

The antenna mast I3 is preferably made of a spring strip material, andis concavely shaped across its width in such manner as to beselfsupporting in its extended portion. The antenna mast material issimilar to the well-known spring measuring tapes which are concave inform across their width, and which may be easily coiled and retractedinto a suitable housing. In this case, the antenna mast I3 is similarlyprovided with a receiving enclosing housing 11 for the retracted orunextended portion of the antenna strip material.

One of the particular difficulties that was encountered in the past, inproviding an adjustable antenna for aircraft, was the fact that theextremely high wind pressure on the antenna imposed a heavy load uponthe operating motor for the antenna mast, and therefore required a motorof relatively large power capacity and correspondingly large weight.

In the present arrangement, I have eliminated the efiect of the windstresses on the antenna by extending the antenna mast upward into aprotective enclosing housing l8 of dielectric material. The housingmaterial may be transparent. The housing is, of course, of sufficientstrength to withstand the wind pressures encountered during flight, andit is provided with suitable flow-line contours to diminish itsresistance. Consequently, the operating motor for the antenna mast needhave but small power capacity, and can be correspondingly small in sizeand of relatively light weight.

In order to position the antenna l3 to provide an extended portion ofproper length and to receive the wave length or frequency that is to bedetected, the electric circuit of the motor is controlled by suitablyeffective limit switches that are disposed to be operated to control themotor circuit when the extended portion of the antenna has attained apre-determined selected position.

The control equipment for the limit switches is also shown in Figure 1,wherein a pinion 2|, on the shaft with the worm gear I5 and the sprocketI6, is meshed with a gear 22 on a control shaft 23 on which are disposedseveral control cams 25-a, 25-b, and 25-c, corresponding in number tothe number of positions to which the antenna is to be adjustablypositioned. The three cams are mounted initially for frictional rotarymovement on the shaft 23, but are held against axial movement, to permitthe cams to be selectively adjusted on the shaft 23.

Each of the three contro1 cams controls an associated pair of switches.Cam 25-a controls the operation of two associated switches 3I-a and32-41 by means of a pivoted operating arm 33--a. The cam -a consists ofa circular disk having a notch or slot 34-a extending radially inwardfrom the periphery of the disk, providing a small recess or pocket intowhich the tip 35c of the operating arm 33a can extend when the cam disk25-a reaches proper position to permit the tip 35-a to enter the slot34a.

The cam disk 25b and the cam disk 25-c are correspondingly shaped andeach disk includes in its control assembly a similar pair of switchesand a similar operating arm, that are identified by the correspondingnumerals as those controlled by cam 25-a but with the subscripts b and0, respectively, as indicated particularly in Figure 4.

In order that the cams may operate properly, to control the associatedswitches, to interrupt the circuit of the control motor, when theantenna has been adjustably moved to the proper position, the cams 25-a,25b, and 25-0 are first selectively adjusted to appropriate positions onthe control shaft 23, and are then held against relative motion on theshaft 23, by suitable means such as a spacer 38 that is secured to thecontrol shaft 23 by a key 39, for example.

The limit switches 3l-a and 32--a, associated with cam 25-11, and theother limit switches that are associated with the other cams, arenormally biased toward their open positions, and are moved to theirrespective closed positions only so long as the associated pressureoperating pins 42 and 43 are respectively pressed inwardly into thehousing for the associated switch. When the pressure is removed fromeither of these pins 42 and 43, the biasing force or restoring force ofthe switch restores the switch to normal open position.

The limit switches may be of any suitable type that will provide thefunctional operation required, as described, but are here shown merelyby way of illustration as being of a type at present available on themarket, that are operable from their normal position to their desiredposition,

such as the closed position, upon the pressing movement of the operatingpin 42, through a relatively short distance, of the order ofonethousandth of an inch. A correspondingly small pressure force issuificient to operate these 4 switches, and the load upon the operatingmotor I l is thus correspondingly held to a minimum.

In Figure 5, the circuit diagram illustrates the manner in which theequipment is controlled to move the extended portion of the antenna todesired position, by the use of a selector switch 45 that embodies acontact arm 46, and three contact buttons 41, 48, and 49, respectively.The control motor H includes a common field winding 50, the armature 5i,and two directional windings 52 and 53, for controlling the direction ofrotation of the motor in opposite directions. Each control button of theselector switch 45 controls the energization and operation of thecontrol motor I I to move the antenna l3 to a respectively correspondingextended position. One pair of limit switches is connected with each ofthe contact buttons 41, 48, or 49 of the selector switch 45. Each pairof switches is controlled by the motor ll, through the cam that isassociated with that pair of limit switches, to insure an accurateextension or retraction of the antenna mast to the proper length,corresponding to each position selected at the selector switch 45.

The limit switches are illustrated in the diagram in Figure 5, in thepositions corresponding to the physical positions shown in Figure 4,when the cams are in the positions shown in Figure 4.

The switches and the cams are shown in Figure 4, at the time the antennamast has reached and is at its second position. The cam 25-?) hasreached its neutral position, at which the operating arm 33-19 is alsoin neutral position, and the associated switches 31-!) and 32h are bothopen at that position, as shown in the diagram in Figure 5. In Figure 4,the operating stems of the two switches are in their respective extendedpositions, under the influence of the biasing forces that move therespective associated switches to open position.

The energizing circuit for the motor I l is therefore open at these twoswitches 3 l-b and 32--b, and the motor will therefore have come to astop, with the antenna moved exactly to the desired length,corresponding to the second position.

When it is desired to move the antenna to either of the other twopositions, that is, to the first position or to the third position, themovable contact arm of the selector switch 45 should be shifted toengage the contact button 41 or the contact button 49, according to theposition to which it is desired to move the antenna.

Assuming that the antenna is to be moved to the third position, thecontact arm 46 will be moved to engage contact button 49, from which thecircuit conductor 55 proceeds to the two limit switches 3I--c and 32-0,connected as shown in Figure 5.

The energizing circuit through contact button 49, conductor 55, andlimit switch 3 lc energizes directional winding 52 of the motor, androtates the motor in such direction as to move all the cams in theclock-wise direction.

The motor circuit, after being thus established, through switch 3 l--c,will be maintained so long as the limit switch 3l--c is closed. Limitswitch 3lc will remain closed until cam 25--c is rotated into neutralposition, where its peripheral slot 34-0 will move into alignment withthe tip 35c of the operating arm 33-c. When such alignment occurs, thecam 25-0 and the arm 33-c will assume the position illustrated in Figure4 as position 2. At that time the limit switch 3Ic will open, and willopen the motor circuit. The motor will thereupon stop, and the antennal3 will stop and remain in the stopped position, corresponding to thethird position for the antenna so long as the selector switch contactarm 46 remains on contact button 49.

While the antenna is in that third position, with the contact arm 46 onbutton 49, the two associated limit switches 3|c and 32-c will be open.The other two cams 25a and 25b, however, will both be in positions wheretheir respective notches or slots 34-a and 34b are to the clock-wiseside beyond their respective neutral positions. Under these conditions,the switches 32-a and 32b for first and for second positions, will bothbe closed. Consequently, when it is desired to retract the antenna backto the second position or to the first position, the selector switchcontact arm will be moved over to engage button 48 or button 41. Thecircuit to the counter-clockwise winding 53 of the motor will have beenalready set up at the switches 32-a and 32--b, and will be completed bythe movement of the contact arm of the selector switch 45 to eitherbutton 48 or 41. When either such operation is made at the selectorswitch, and the motor is consequently energized through thecounter-clock-wise winding Shiite some 53, all of the cams will berotated in a counterclock-wise direction until the cam 25--a or the cam25-47 reaches its respective neutral position, depending upon whichposition was selected for the readjustment of the antenna.

Thus, by means of the cams 25-a, 25-1), and 25-0, and the co-operatingpivoted arms 33-0, 33--b and 33--c, the limit switches may be accuratelyand sensitively controlled to move the antenna to the exact positionthat is desired, without any hunting or over-travel.

In the functional operation of the cams as illustrated schematically inFigure 4, it will be clear that each cam is respectively controlledaccording to its position on the shaft. After each cam is adjusted toproper operating position, the operating pin 40 on each spacer 38, isnot needed.

In order to aid in the adjustment of each cam to predetermine itsneutral position, according to the frequency to which the antenna is tobe adjusted, a frequency dial B is fixed to shaft 23.

For simplicity of operation and other obvious advantages, the selectorswitch 45 may be arranged for gang or mutual operation with thefrequency selecting switch 56 on the radio equipment 51 that uses theantenna.

In Figures 2 and 3, the arrangement is shown whereby the antenna mast I3when extended to its extreme position in the housing I8, is caused toengage and enter the jaws of a contacting clip 60 that constitutes aterminal for a horizontal antenna wire ii for reception of longer wavelengths than the antenna 13 is intended for. The antenna BI is shownsupported between the housing l8 for the antenna mast l3, and astructural part of the support 52 for the rudder, at the rear of theplane.

By means of the arrangement shown, the antenna mast I! may beselectively and automatically extended or retracted to any one ofseveral predetermined tuning positions, while protected from windpressure. motor is thus reduced; to a minimum, and the size and weightof the motor and of the associated control equipment may becorrespondingly reduced to a minimum;

Although I have referred to the antenna as used forreceiving operations,it may equally well be used for transmitting. The enclosing housingstrut being a dielectric, may be made of transparent material. By meansof such enclosing housing around the antenna, wind pressures on theantenna are prevented, and any resistance resulting from the presence ofthe housing is reduced to a minimum by streamlining of the housing.

My invention is notrlimited to the specific details of the constructionas is shown in the specific arrangement and location, since variousmodifications may be made therein without departing from the spirit andscope of the invention as set forth in the appended claims,

I claim:

1. An antenna system for aircraft, comprising a rod mounted for movementinwardly and out- The operating load on the wardly of the aircraft, ahollow fixed-length ing the motor selectively thereby determining thedegree of projection or retraction of said rod.

2. An antenna system for aircraft, comprising a rod mounted forreciprocation relatively to the aircraft, a fixed-length streamlinedhousing :lnounted contiguous to the upper end of the rod, a reversiblemotor mounted contiguous to the lower end of the rod and in electricalcircuit with the electrical source in the aircraft, powertransmittingconnections between the motor and the rod, circuit-controlling meansterminating adjacent the pilot for causing the motor to, run in eitherdirection to raise or lower the rod within and longitudinally of saidhousing, and means for automatically breaking the circuit when the rodapproaches extreme limits of travel,

3. In combination, an all metal aircraft fuselage, a rigid antenna rodmounted for reciprocation inwardly and outwardly of said fuselage, a.hollow-fixed housing positioned exteriorly of the fuselage in alignmentwith the path of movement of said rod and into and from which it may beprotracted and retracted, and means under the control of the pilot toregulate and determine the protracted or retracted positions of the rodwith respect to said housing and the fuselage.

4. An antenna system for aircraft comprising a rod mounted forreciprocation relative to the aircraft, a fixed-length streamlinedhousing mounted contiguous to the upper end of the rod, a reversiblemotor mounted contiguous to the lower end of the rod and in electricalcircuit with the electrical source in the aircraft, powertransmittingconnections between the motor and the rod, circuit-controlling meansoperable from within the aircraft for causing the motor to run,

in either direction to raise or lower the rod within and longitudinallyof said housing, and means for automatically breaking the circuit whenthe rod approaches extreme limits of travel.

JAMES KELLER. DE Armour).

REFERENCES orrnn The following references are of record in the file ofthis patent:

UNITED STA'I'ES PATENTS Number Name Date 2,062,129 Hefele Nov. 24, 19362,222,588 Williams Nov. 19,1940 2,283,524 White May 19, 1942 2,313,046Bruce Mar. 9, 1943 2,368,298 Harris Jan. 30, 1945 2317.191 Fox Mar. 11,1947

